Search This Blog

Wednesday, 27 July 2016

Snubbing the Nordfrost Freezer

We have a small chest freezer in the house. A Nordfrost one. We have had it many years, and it has been ok, but it has required a new thermostat as the contacts on the old one burned out. And every time the compressor shuts off, it interferes with the TV, causing a momentary jerk in the motion, or pixelation, or a slight glitch in the sound.

When an inductive load is switched off, the energy stored in the magnetic field (in this case in the windings of the motor) tries to keep the current flowing, developing a big voltage across the switch contacts and causing an arc. The arc is like a spark-gap transmitter and generates radio interference. The solution, it seemed to me, was to fit a "snubber circuit" which is a capacitor in series with a resistor wired across the thermostat contacts. The energy which would have caused the spark now flows into the capacitor and is dissipated in the resistor.

I measured the inductance of the compressor - 43mH. I also measured the current drawn by the motor - 0.66 Amps. Then I calculated the energy stored in the inductance, which is "a half L I squared", or 0.5*L *I^2. There is a similar equation, "a half C V squared", (0.5C*V^2) for the energy stored in a capacitor, and I reasoned that I needed a capacitor to store about the same energy as was in the inductor. It worked out at 315nF. I had a couple of 220nF capacitors in the junk box. Importantly they were X2 rated capacitors (see the marking in the photo below) which are suitable for connecting directly across the mains.
These X2 metalised film capacitors are "self healing" - if the dielectric starts to break down the internal spark evaporates the metal on the plastic film and the area of broken-down dielectric is isolated. Some types of capacitor can fail with a big bang and a puff of smoke when the dielectric fails.

When I looked on the internet there was a lot of stuff about designing snubbers for MOSFET circuits, and Switchmode powersupply circuits. They all said that the time constant of the C and the R needed to be about 10% of the "on time". Not sure how that relates to a thermostat, but the mains frequency is 50Hz, and so each cycle is 0.02 Sec. The time constant of my 220nF cap with a 10k resistor is about 0.002 Sec so I plumped for a 10k resistor. The time constant is calculated by multiplying the C by the R. And it is the time taken for the capacitor to discharge to about 30% of it's starting Voltage when discharging through the resistor. It probably doesn't matter much as long as there is some resistance to dissipate the energy.

When the motor is not running the snubber will have quite a lot of Voltage across it - most of the mains Voltage. A 220nF capacitor will pass quite a few milliamps at 240V. It is possible to work it out with phasor diagrams and power-factors and things, but I simply connected the circuit across the mains and measured the Voltage across the resistor - which was about 135V. Since power = V squared over R, that is about 1.8 Watts being dissipated in the resistor. In fact it will be less, because the motor is in series. At first I paralleled up 10 x 100k metal film resistors, but that is quite a fat bundle. I found it was better to series 10 x 1k resistors and cover them with heatshrinkable tubing. Each resistor is good for about 0.6W, so in theory my chain should be ok dissipating 6W, but it is good to have some margin of safety. The long thin arrangement dissipates the heat better. I put five on each leg of the capacitor.
So I had an arrangement like this:

The Nordfrost thermostat is mounted in a plastic box in the front of the cabinet, so it is quite easy to get at - there is also a fair amount of room inside the box to accommodate extra components. I used some of the "piggy-back" type 1/4" push-on connectors to connect the snubber circuit. Since these just crimp on to the wires there was no soldering to do. Here's a picture with the cover removed - there is rather a tangle of wires, but nothing is danger of shorting to anything else so it is ok!
So I installed the snubber this evening, and we have been watching TV. Here's the interesting thing. The interference when the freezer turns off has completely gone ... but ... there is sometimes a bit of picture disturbance when it turns ON !  Not sure what is going on there. I wonder if it is something to do with the PTC starter circuit on the compressor - which is an extra winding on the motor that is connected at switch on, but is disconnected by a "Positive Temperature Coefficient" resistor once the motor is running ... I need to think about this.

The other slight downside to the snubber circuit is an increase in power consumption - the result of having a small current flowing in the resistor when the motor is off - I guess it is about a Watt of electricity wasted during the off period of the freezer.

Perhaps an in-line RF filter might help with the TV interference.
At least the snubber should extend the life of the thermostat contacts.


Monday, 13 June 2016

Simulating the FIlter in the Microphone

Having measured the values of the filter components in the Retevis Speaker-Mic, I thought it would be interesting to simulate the circuit and find out roughly what the cut-off frequency was.
I use the free simulation software from Linear Technology, called LTSpice.
Here is the circuit ...
At this stage I used 50 Ohms for the input and output impedances, and got this nice curve:
The cut-off is surprisingly low at around 5Mhz but the attenuation at 433MHz is (in theory) 120dB.

However ... the input impedance is the input impedance of the audio input of the radio, modified by the long curly lead and jack plugs. The output impedance should match the input impedance of the electret condensor capsule. Both of these are unknown, and only really measurable with complicated test gear. But I know the capsule measures about 2000 ohms with a Digital Volt Meter, so I did another simulation using that impedance.

I also extended the lowest frequency down to 100 Hz to see what was happening in the audio range. It is very different. However the flat response up to 100kHz will still pass all the audio frequencies ok, and the filter still appears to offer significant attenuation in the UHF region.

The dashed line, by the way, is the phase response, using the scale on the right hand side. The solid line is the amplitude response using the decibel scale at left.

It would appear that the designers of the filter may have simply designed a 50 ohm impedance filter and hoped it would do the job.

Another thing I noticed when measuring the inductors on the board was how low the Q factor was. The meter said 0.031, with a series resistance of 0.186 ohms. It made me wonder whether the inductors were of the conventional kind, or whether they were the special EMI absorbing sort, like these from Wurth Electronics WE-CBF SMD EMI Suppression Ferrite Bead
I think these tend to be deliberately lossy to absorb the RF energy, while at the same time having a low d.c. resistance. There are no markings on the parts fitted on the board, so it is difficult to tell what they are. One would normally expect the Q factor of a surface mount inductor to be, say 30 - 40.

Still not sure what to put in my hands-free set-up!

Saturday, 11 June 2016

Microphone and Speaker Connections for TYT MD380

Just over a week ago I bought a new radio, a TYT MD-380 DMR handheld. A new repeater, GB7AS has just opened, about 6 miles from here, and I am keen to access it because it has very good coverage in this area. Indeed, with the links to other repeaters in Kent it should provide opportunities to work many of the amateurs in the the Folkestone area that have been in the shadow of the North Downs for me here.

There is plenty of information about DMR on the Internet already ... although, later, I may blog a bit about using the programming software. I need to get to grips with it myself, first!  One of the things I wanted to do was to make a hands-free set up for the car so that I can take it mobile. However the manual contains no pin-out information for the microphone and speaker, and I couldn't find much about the subject on the web. The situation is complicated by the fact that the same sockets are used for a USB programming cable. So I thought I would write a bit about that here.

I decided to buy an inexpensive speaker mic for the radio, and use that to find out what the connections are. So I bought one of these:
It is a Retevis 2 Pin PTT Speaker Mic for TYT MD380 (and other radios).

Picture of it plugged into the radio at left.

The microphone is surprisingly small, but quite comfortable to use. The sound is even more thin and tinny than that from the radio, which already has a sharp and penetrating quality.

In the photo at left, just where my little finger is and where the cable enters the microphone body, is a socket to plug in an earphone. You can see this more clearly in the photograph of the circuit board below.

There is a useful clip on the back which partially obstructs the top screw, you need a well-fitting screwdriver to avoid slipping out of this.

The PTT button has a nice feel to it with a tactile click to let you know the contacts have closed.

After plugging in the speaker mic and checking that it basically seemed to work, I set about removing the screws from the back.

There are a further three screws to hold the circuit board to the moulding, and you need to be careful not to loose the little rubber pad which goes between the PTT lever and the button on the board.

Quite a nice PCB inside, with rather more components than I expected.

Tracing out the circuit, I can see that the surface mount capacitors and inductors are for filtering. Now this is interesting, because I have always taken the approach that you want to prevent RF from entering the microphone socket of the radio, but here the filter seems to be preventing RF from entering the Microphone capsule. Since all electret condesor mic capsules contain a little pre-amplifier (usually just a FET transistor), RF voltages picked up on the microphone cable could potentially demodulate in the microphone. The situation is made worse by the fact that the microphone is likely to be used in very close proximity to the aerial. I have traced out the circuit, but not yet measured all the values. The measurement of the L's and C's requires their removal from the board as the other components affect the reading on the meter.

The connections are helpfully marked on the PCB, so all that was required was a continuity test to find which part of the jack plug was connected to which wire in the microphone. The unused (tip of the 3.5mm plug and ring of the 2.5mm plug) are presumably for the USB programming connection.

I note, from the specifications in the radio handbook, that the audio output is 1W into 16 Ohms. I measured the d.c. resistance of the speaker to be 10 Ohms - suggesting probably IS a 16 Ohm part (The d.c. resistance of a speaker usually measures a little lower than the a.c. impedance, as the latter includes the inductive reactance of the voice coil).

At this stage, I am not sure whether to include the filter circuit in my hands-free set-up. In the car, the antenna is further away from the microphone, so the fields should be much less. I may just put some small capacitors across the mic and see how well it works.

The other question I need to mull over is whether to get hold of a 16 ohm loudspeaker, or to try using the 3 ohm speaker that I am currently using in the car. If a 16 ohm speaker is not available, I guess I could build myself a little audio amplifier - but that adds extra complexity and would need a 12V feed from an accessory socket in the car.

So that is the story so far. I hope my look at the audio connections might help you make useful accessories of your own.

Hugh M0WYE

Update 13/6/2016: I measured the component values in the filter circuit and added them to the circuit. Also corrected a slight mistake where the PTT button connects to ground.

Saturday, 28 May 2016

DX TV signals from Poland

The Sporadic E season is well and truly "happening" with an opening to Scandinavia on the 25th, when I worked SM5ZCJ, OZ2KEC and 9A2RD all on 6m. The next day it was even better, and I worked SM6CXS, YL2SW, ES5QD, LA5YJ and YL2GP. On this day I heard 2M0UAL working another UK station, this Scot was only 520 miles, much less than the usual 1000 miles. A shortening skip distance often indicates that higher bands are open too and Facebook posts on the 70MHz group confirmed that that band had been busy too.

Last night was fairly quiet, although I did work EA7JUR (and his pet cat).

Well today, it has been Poland coming through loud and clear. I worked Roman SP9RM and Bogdan SP4LVC. While I was waiting for my chance to work Bogdan, I noticed that there was a buzzing sound, which is TV frame buzz. It is quite distinctive because the sound of the buzz changes each time the camera angle changes. So I quickly got out my 5" black and white portable TV set and connected the 6m antenna to it.

I was quickly rewarded with, first synchronisation bars, and then, pictures. Well they are pretty grainy, but at times they were clear and watchable.

I also tried to make a little video to show how the pictures were constantly fading in and out. I put that up on Youtube, here.

Unfortunately, in Europe, the TV frame rate is 25 frames per second, which doesn't work at all well with the 30fps frame rate of the camera. The result is an unstable image with black bars which weren't on the original... but it kind of gives the idea.

For the record, my antenna is very simple, just a 1/4 wave ground plane - that's a 1.5m long whip, poked through a hole in the ridge of the roof. The felt underneath the tiles has an aluminium foil covering, and that is connected to the shield on the coax, so the whole roof becomes a ground plane.


Wednesday, 18 May 2016

External Speakers on FT847

When operating a special event station it is useful if the visitors can hear the audio output of the radio, and it is also useful if the operator can wear headphones - because there is always chatter and other noise going on in these places. But, when you plug headphones into the Yeasu FT847 the loudspeaker is switched off, so no one else can hear.

I found a fairly easy way round this. There is a second audio output available on the rear of the radio which has a 200mV output level, that is independent of the Volume control on the front panel. This is on a stereo 3.5mm jack socket marked Data In/Out. It is intended for connecting a packet TNC, or other data-mode device to the radio, but the audio quality from this socket is good.
Red arrow shows the Data In/Out connector on the back of the radio.

 The output is about the right level to drive a pair of PC speakers, but there is a snag ... The audio out is on the ring of the jack and the tip is used for PTT and for audio in, so if you plug the stereo plug from the speakers into this socket the radio goes straight into TRANSMIT! This is because the input impedance of the speakers is sufficiently low to make the radio think that the "TNC" has selected transmit. So I made up a simple adaptor out of a plug and socket, wired as shown below ...
Do test the speakers with the radio on transmit before using them at the event, because PC speakers are notorious for being sensitive to RF fields and may demodulate your SSB transmissions in an unpleasant way! Fortunately the speakers lent to us by Chris, G6AFY, were of high quality and behaved very well.
So here is a picture of me operating GB8WW with my FT847 and the PC speakers plugged in the back, the stylish, wedge-shaped thing in the foreground. If you look carefully you can see the adaptor-lead plugged into the back of the radio.

The headphone volume is controlled by the AF gain control on the front of the rig and the PC speakers are controlled with their own volume control.

One of the criticisms of the FT847 is the "steppy" digital AF gain control on the rig, making it hard to get the right listening level - so using an external speaker on this audio output might be a way round this in the shack - so this adaptor might be useful for more than the occasional special event station.

Happy Operating, and 73
Hugh M0WYE

Monday, 2 May 2016

Headset adaptor for FT847

It is nice to have both hands free when using the Amateur Radio - especially when operating a Special Event station or contesting, because you can fill in the log, and fiddle with the radio controls while talking. And  ... your thumb gets tired using a fist mic!

With the popularity of gaming and Skype, some nice headphones with microphone booms are available quite cheaply. I bought one of these: "Gearhead" AU3700S Computer headsets for £10.91. This one has 3.5mm stereo jack plugs for the microphone and headphones. I noticed that quite a lot of the headsets now come with a USB plug, which presumably has a USB soundcard built in. Not much use if you want to connect to an old analogue wireless set! Make sure you get one with jacks.

The headset is actually terminated in a "four ring" jack plug, suitable for Apple devices (apparently) but comes with a Y adaptor with a separate plug for headphones and microphone.

To use the headset with a radio we need some kind of adaptor box. This will have socket(s) for the headset and leads to plug into the microphone and headphone sockets on the radio. It will have a Transmit/Receive switch or PTT button, and with supply a bias Voltage to drive the electret condensor element in the microphone.

So this is what I built. I decided to stick with the "Y" adaptor on the headset, because it means that the box becomes more versatile having separate sockets for mic and headphones. I wanted the box to be well screened because there maybe high RF fields around, so I used a diecast aluminium box, from Hammond Manufacturing (Pt. No. 27969PSLA) - it is one I picked up last year at a Radio Rally. I found some flexible 9-way screened cable - more conductors than needed but I doubled up the ground connections to try and keep the impedances low.

But we have to be careful not to introduce ground loops. There is the cable screen, there is the microphone ground, there is the headphone ground and there is the PTT ground, and really they should all be kept separate. Trouble is a lot of jack sockets have a metal fixing nut that connects the barrel of the jack to the metal box that they are mounted on.
Fortunately I found some inexpensive, 3.5mm Jack sockets on E-bay which have a single (8mm dia) hole fixing, but are completely insulated from the metal panel.

Gold-plated too!

The FT847 manual has a useful diagram showing the microphone connections. The headset connections are fairly standard - in fact there is an industry standard which specifies the microphone and speaker connections. On the microphone the tip carries the signal and should be capacitively coupled, the ring carries the bias Voltage which must be less than 5.5Volts and sourced from an impedance greater than 2.2 kilohms. I used a 10uF solid aluminium electrolytic capacitor and a 3k9 resistor for coupling and bias resistor. Seems to work well.
Here is a circuit - drawn on CAD as you can see :-)
The mic connector is viewed looking at the front-panel of the radio. So it is viewed from the solder-terminal side of the (female) microphone plug.

The "spare" pins on the mic connector are used for "up" and "down" buttons on the microphone - but I haven't used them here.

The headphone circuit is kept completely separate - partly because the radio offers the facility to listen to your own SSB transmissions, so we don't want any audio getting back into the microphone socket. I used RG58 for the interconnecting cable, as we only need a mono signal for the 'phones.

the TX/RX switch is just a bog-standard DPDT toggle switch.

So here are a couple of pictures of the "innerds".
 I have tywrapped the incoming cables to the body of the jack socket. There may be more elegant ways of strain-relieving the cable but this seems to work ok.
The big fat grey wire, is actually the braid from the multicore cable being soldered to a solder tag on the die-cast box. Might have been better if this was a shorter connection from an RF screening point of view, but hopefully it will keep HF frequencies out of the box.

The finished box looks like this:

On air reports have, so far, been favourable. One thing to note is that the output of the electret condensor mic is much higher than the standard fist mic supplied with the radio. I used a deviation meter to check the FM modulation level, and found that I had to reduce the FM microphone gain from 32 to 12 in the menu system. Menu 25 [FM-PSET]. I also went through the procedure for setting the SSB microphone gain - setting the meter on the rig to measure ALC using Menu 24 [TX-MTR]. Strangely the SSB mic gain is set close to where it usually is. The "Moni" feature on the radio is great for listening to your own input, you can set the Monitor Volume using menu 20 [MONI-VOL] - but unfortunately you can't monitor when using the speech processor as it uses the same circuitry!

So there you have it, a Bank-holiday-Monday headset to FT847 adaptor box.
Hugh M0WYE

Further notes

The 3.5mm Jack is an EST Part: Part no. MJ073H, from Ebay, here

8 pin microphone connector also from Ebay:
But found the thread on the locking ring was poorly made, and won't screw up on the socket - so I will have to change it ... a pigging nuisance!

Wider transmit range on FT847

Some years ago UK Radio Amateurs were permitted to use the upper part of the 40m band, 7.100 - 7.200MHz. Many older radios, sold in the UK, such as my FT847, restrict the transmit range to what was previously legal, 7.000 - 7.100 MHz. It is rather frustrating when you can hear QSOs or CQ calls, but when you press the transmit switch you get a "beep" and an error message. Doubly frustrating when you know the circuitry is quite capable to transmitting and radios sold in some territories, such as the USA, do cover that part of the band.

I wanted to use the radio during the forthcoming "Mills on the Air" special event station, GB8WW, and it seems that the 40m band is used a lot for Special Events, so full coverage would be essential.

"Widebanding" radios, modifying them to transmit at any frequency, is quite commonplace, but requires the operator to take great care not to transmit outside of the band where they are legally allowed to. With the FT847 there is a further complication. The radio covers VHF and UHF as well, and the programming links which set the TX limits also affect the repeater shifts and the radio's ability to transmit on the 70MHz VHF band.

Fortunately G1IVG has put a useful table on his website, here, which shows the different ranges available. The programming links are on the PCB next to the memory backup cell. You can see them, numbered from 1 to 6 in this picture.
 The links look like surface-mount resistors, but are actually "zero-ohm links", and can be replaced by blobs of solder or very short pieces of wire. You can see that links 1, 2, 5 and 6 are shorted and links 3 and 4 are open. (Always useful to take a photo before you make a modification so you have half a chance of putting it right if it doesn't work!).

Looking at G1IVG's table you can see that there are only two link settings where the radio has the 70MHz band, the first is the standard UK configuation that I have, and the second one has links 1,2 and 6 shorted and the others open.  The HF options are in the table below, and this link combination gives the HF bands in row 5.











All the HF bands, except topband and 10m, are made 500kHz wide - so one still has to be careful not to transmit out of band, but, the problem of the 40m band is certainly solved by this. It doesn't allow the radio to operate on the 60m band, but (at the moment) this doesn't interest me much.

The 2m and 70cm bands become very wide, 140 to 154 and 420 to 450 Mhz respectively, so again, some care will be needed when operating on VHF too.

Performing this mod wipes all the channel memories and any changes you may have made in the menu system (display brightness, channel steps etc.), I already had a list of all my channels, with the CTCSS frequencies, repeater offsets etc, but I went through the menu system and carefully recorded all the settings there too.

So... I chose the finest soldering iron bit, found my tweezers and strongest reading-glasses, and set to work. Instead of removing the link 5 completely, I turned it round, so that it is still attached to the ground pad. That makes it easier to undo the mod, or reuse the link on a different pad if I need to.

The photo at left shows link 5 under a magnifier.

The links are only read by the microprocessor at factory reset, so it is necessary to hold down the "lock" and "fast" keys when you power up the radio for the mod to take effect. This is why all the all the channel memories are erased.

I turned the power control down to minimum, attached dummy loads to all four antenna sockets and carefully explored the frequency ranges. I am pleased to report that the new transmit ranges seem to match up with those in the table.

The repeater offsets basically match up with the UK standard settings, except for 50MHz where the offset is 1MHz instead of 500kHz. This is configurable in the menu system. So it all seems quite promising, and the radio is "good to go" for Mills on the Air 2016.

Hugh M0WYE

Wednesday, 13 April 2016

ISS SSTV, Second Pass

Two part-pictures received on the 8:19pm pass.
 This one faded into the noise as the ISS dissappeared over the horizon ...
Very nice visual sighting, with the station coming within a few diameters of the Moon and then passing very close to Jupiter in the twilight sky.

Slow Scan Television from the International Space Station

It was a nice surprise to get an SSTV picture from the ISS on its 6:43p.m. pass.
I think the Russian Cosmonauts are commemorating the first Amateur Radio contacts aboard the ISS by sending SSTV pictures like the one above. I was using the free MMSSTV software, with the 2 meter radio connected to the sound card input. But for some reason the software didn't automatically select the correct mode (PD180). Fortunately I had a little Olympus voice recorder recording the sound from the speaker, so I was able to feed that back into the sound card and get the picture above.
The data compression might account for some of the patterning on the picture.

The transmissions are on the usual downlink frequency of 145.800MHz. You can read about how to do it on the AMSAT website here. But you don't need anything more sophisticated than a scanning receiver speaker output connected to the sound card line input. I just use my normal "white stick" colinear antenna, but a 1/4 whip, or even a rubber duck should pick something up.

I use the Orbital Prediction Page on the AMSAT website to find out when the ISS is coming over.

Saturday, 12 March 2016

Anatomy of a Trifle

Two boxes of Trile Mix - Strawberry Flavour.
Some other ingredients.
Swiss roll, with jam and cream. Chop it up so everyone gets a bit.
Add the strawberry jelly. Put in the fridge to set.
Separate the peach slices from the liquid and chop them up a bit.
Peach slices on top of the jelly
Add lots of custard.

To be continued ... !

... Early next morning !
 Moroccan raspberries are actually a bit disappointing, some nice raspberry flavours, but little sweetness. Hopefully be ok with all the other sweet things in the mix.
Bon apertit and 73
Hugh M0WYE

Windows Vista Automatic Update Problems

Since fitting the SSD the computer is very quiet, so , one evening,  my attention was drawn to the sound of the fan whirring. An investigation with Windows Task Manager revealed that wuauserv was running. This is the Windows Automatic Update service. It was using 50% (one core) of the CPU. After an hour I got fed up with it and started Windows Update manually to see what was going on. It just sat on "checking for updates" ... And nothing happened for another hour.

So I gave up and disabled auto updates.

Looking on some computer forums, it seems that others have had issues with the wauaserv locking up. But if your auto-updates are broke there is not much chance of downloading an update to fix it.

On one forum I found "Windows Offline Update" was a solution, so I decided to try it for myself. It is not Microsoft, it is Open Source. It allows you to download all the updates for a particular version of Windows, and copy them onto, for example, a USB stick. Then you can install all the latest updates onto a machine which is not connected to the Internet. I was attracted to it because it gives a bit more control over the update process.

So I downloaded it from here:

There is a very good tutorial about it by Eli The Computer Guy..
It is worth watching this before attempting to use the software.

I found there were 2.5 GB even without the Office 2007 updates, so be prepared for a big download. The software worked very well, with a Windows "front end" that has check-boxes to select what you want to download or install. When you have made a selection some sort of script starts in a "command line" style box. Each step of the process appears on the screen and is logged to a file.

Although I had expected the offline updater to use its own software, it actually seems to use Windows own routines for at least some of the work ... including the dreaded Wauaserv! And, when a line appeared on the screen saying something like "building I.D. list of required updates", nothing happened for a very long time ... nearly 2 hours, in fact. If it hadn't been for the additional message which said "this may take a long time, please be patient" I would have aborted the process. The updater found, and applied, 19 updates.

This kind of software would be ideal for a computer repair shop where many computers have to be updated. Also if you have to reinstall windows, it might be useful to have the complete set of updates on a DVD or memory key.

For myself, I need to learn "patience", when wauaserv " locked up" it was probably just halfway through checking what updates were needed. Will we reach a point when our computers can do nothing else but install updates all day long!

I will probably go back to using Windows Update, but do so manually, putting up with the red shield symbol and the nag messages at boot-up. It won't be long before Microsoft stop supporting Vista anyway.

Hugh M0WYE

Fitting a Samsung 850 EVO 250Gb SSD to the Inspiron 1525 Laptop

So last time I told you about increasing the size of the RAM. Now to actually fit the SSD.

Again there are Youtube videos which show you how to do this on the exact same model of computer so there is little point in me going into great detail about that here:
Youtube video showing how to change the Hard Disk
The computer guy is fitting an EVO 840 SSD, but it seems identical to the Samsung 850 EVO 250Gb SSD I bought from Amazon.

If you watch this video you will see that the guy making it has problems getting the connector on the hard disk to make proper contact with the socket in the computer. The problem is that the SSD is slightly slimmer than the old hard disk and the SSD needs to be lifted slightly when you slide it into the slot. It is confusing because when the SSD misses the connector it still slides fully home and almost feels as if it has plugged-in. When you power-up the computer you get a message saying "No boot device available".
Our solution was cheap and simple and required a small piece of cardboard cut from the Amazon carton that the disk arrived in ... and some sticky-tape. See photo below ...
The cardboard has been folded over so there are two layers.
The photo also shows the Samsung SSD mounted in the tray which is part of the computer. It is necessary to take the tray off the old disk and fit it to the new one. There are just two small screws holding it on.
The photo below shows the disk ready to be refitted to the computer, you will see that the cardboard is on the bottom, so it lifts up the end of the disk as it slides into the slot.

The two black screws in this picture are the ones which secure the tray into the computer after you have fitted back in the slot.

So really the mechanics are very simple. However I should emphasize the need to SHUT DOWN the computer before changing the disk drive (or the memory) - don't just hibernate it. And take out the battery too - some parts of the motherboard could still be powered and also the computer could be started accidentally if a button is pressed when handling it.

The other part of the process is the "cloning" procedure. The Samsung SSD comes with a CD or DVD of software to do this, but we used some other program that my son had already used to do clone his laptop disk.  It is called Macrium Reflect Free and is a free trial.

Before doing any cloning, it is a good idea to uninstall any unused software and do a Disk Cleanup. In fact we managed to free up about 50Gb of disk space (a big chunk of that was FlightsimX which was no longer used).

We plugged the laptop's old disk and the SSD into a desktop machine that had several spare SATA interface sockets. Our attempt at using a USB to SATA lead (bought from Ebay) failed part-way through the copying procedure, we are not sure why, but it is much quicker to use a direct SATA connection anyway. So that is what I would recommend if you can get access to a suitable desk-top PC.

The performance is greatly improved - particularly the time taken starting applications. Windows Mail is on of the applications that is most transformed - I'm not quite sure why, but it checks the E-mail much faster now. (This might be related to Kaspersky Internet Security checking all the E-mail).

The computer is almost silent for much of the time ... only the fan running. It was the noise of the fan which prompted me to investigate why Windows Update used so much system resources ... but perhaps I will tell you about that on another occasion.

Hugh M0WYE

P.S. After fitting the SSD go into the Defragmenter and turn off any scheduled defragmentation. A Solid State Disk doesn't need defragmenting, and it may actually reduce the life of the disk. Plus ... it will be one less thing that the computer is doing "in the background"!

Upgrading the Dell Inspiron 1525 Laptop Computer

I thought I would tell you a bit about my experiences of upgrading my Dell Inspiron Laptop. I Have been using this for many years and have been very happy with it. It runs Windows Vista, which a lot of people don't like, but it has worked well for me, and, frankly, a well patched copy of Vista seems very little different to Windows 7. 

A popular upgrade for any laptop is to fit a solid state hard disk. A lot of the slowness of any computer seems to be caused by disk access. This computer has a 250Gb hard disk which is getting pretty full, a Samsung Evo 850 250Gb SSD was available for about £60, which seemed very good value. I back up onto a 1Tb external disk, but to have a "spare" disk which is a exact clone of the disk in the computer is a tempting extra benefit of performing this up-grade.

The only down-side to using Solid state disks is the limited number of write cycles that can be performed. It numbers in the 100s of thousands, and modern disks have clever software which spreads the data around on the disk, minimising wear to any particular part. When memory is low, Windows uses "virtual memory" where it uses part of the hard disk as an extension of RAM. A computer which has limited RAM will make many more reads and writes to the hard disk. Obviously this can be reduced by maximising the amount of "real" RAM fitted to the computer. So before fitting the SSD I decided to do that. There are two "slots" in this Laptop and they were both occupied with 1Gb modules. The largest size you can fit to the Inspiron 1525 is 2Gb which gives a total of 4Gb.

Access to the memory is very easy, there are eight screws to remove and then you lift off a panel on the underside of the computer. There are a number of Youtube videos about this so I won't go into great detail here. This is the one I found best: Youtube Video shows how to change the RAM in a Dell Inspiron 1525 Laptop. You can see the pair of memory modules in the photo below, together with the heat-pipe leading away from the processor and the WiFi module among other things.

I will say a word or two about my choice of replacement RAM modules, or "SODIMMs". When I looked for replacement RAM on the internet,  I found there were some websites where you punch in the make and model of your computer and the website recommends the "correct" type of module to buy. I was going to click "Buy Now" on one of these, but then thought I should check what was already fitted.

The site had recommended PC2-5300 modules, but if you look at the picture below, you can see that PC2-6400S modules are fitted.

So this worried me, and I decided to try and find out a bit more about the numbers on the modules. The Wikipedia article on DDR memory is quite useful in this respect: Wikipedia Article about DDR memory. The 6400 RAM seems to be slightly faster than the 5300, so that was what I decided to fit, even though it was a bit more expensive. Indeed, I looked for some RAM modules by the same manufacturer, Hynix, because I reasoned that near identical, but larger, modules would give the least opportunity for incompatibility. As an electronic engineer, I have sometimes encountered small differences in spec between two components made by different manufacturers that can cause annoying problems.
As you will see below, I have fitted two Hynix DDR2 PC2-6400S modules and they work absolutely fine. 

Incidentally, the "S" on the end of 6400 seems simply to mean "Small" and refers to the fact that these are laptop modules, and not the slightly larger form of SODIMM used in Desktops. Also the 2Rx8 and 2Rx16 numbers seem to be unimportant, and would appear to refer to the number of ICs on the SODIMM.

Next, I'll tell you about the Solid State Hard Disk ...
Hugh M0WYE

Friday, 26 February 2016


A nice E-mail from Ofcom arrived with a Notice of Variation attached to it. This permits operation of a special event station GB8WW for the Mills on the Air weekend, 14/15th May 2016. So we are looking forward to a bit of portable operation at the Open Day for National Mills Week at Willesborough Windmill. I found and scanned a nice picture I took at an open day in 1994 - not much has changed!

Hoping to operate the station with my good friend Peter, G8WMZ, and any other willing volunteers who can be found.
Hope to work you on the air in May. 73
Hugh M0WYE

Friday, 12 February 2016

Tim Peake ARISS Contact

Used my Yeasu FT60e and an HB9CV to listen to astronaut Tim Peake as he conducted a  schools contact with a school in Rickmansworth.
The clear sky gave a good visual pass, so pointing the antenna quite easy ... manual satellite tracking. I made an audio recording that I have edited into a YouTube video, here...

Friday, 5 February 2016

Making Plastic Objects at Home

After a seeing a comment about some rather tough Jarlsberg cheese on Facebook, I was reminded that milk was once used to make a kind of plastic - casein plastic was used for buttons and other small items. Manufacture of this material is possible at home. I turned to my copy of "Chemistry Experiments at Home for Boys and Girls" - a 1949 book by H.L.Heys M.A. (Cantab). Such publications as this would not be encouraged nowadays, but in 1949 making plastic objects in the kitchen was aparently well within the abilities of school boys and girls.  Here is the recipe...

73 Hugh